Multiway regenerative repeater system



Sept. u, 1949.

K. E. FITCH MULTIWAY REGENERATIVE REPEATER SYSTEM 3 Sheets-Sheet l FiledAug. 25, 1945 ATTORNEY Sept. 139 1949. K. E. FITCH 2,481,919

MULTIWAY REGENERATIVE REPATER SYSTEM Filed A ug. 25, 1945 5 Sheets-Sheet2 REGENERAr/vs @EPL-'ATER 4 /03 l l y /09 POLARZED DOUBLE SPACE HY PASSIIN/' /NVENTOR K E F/ TCH By JM f. CM-yn ATTORNEY Sept- 13, 1949 K. E.FrrcH MULTIWAY RIEGEERA'IIVE REPETER SYSTEM 3 Sheets-Sheet 3 Filed Aug.25, 1945 lll l l l patented Sept. 13, 1.949

MULTIWAY REGENERATIVE' REPEATER SYSTEM Karl E. Fitch, Summit, N. J.,assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a corporation of New York Application August 25, 1945, Serial No..612,679

12 Claims.

This invention relates to telegraph repeaters and more particularly toan improved multiway regenerative telegraph repeater.

An object of the invention is the improvement of telegraph repeaters.

A more particular object of the invention is the improvement of multiwayregenerative repeaters.

By a multiway regenerative telegraph repeater is meant an arrangementwherein more than two telegraph lines or loops, each equipped with anindividual telegraph repeater, are interconnected through a hub into ahalf-duplex concentration group served by a single regenerative repeaterunit in such a manner that any one of the individual telegraph lines orloops can transmit through the single regenerative unit to all of theother interconnected lines or loops simultaneously. As is well known inthe art when telegraph signals are transmitted over long lines, whichmay include telegraph repeaters of the nonregenerative type, they tendto become distorted. It is therefore necessary at times, before furthertransmission is feasible, to transmit the signals through a regenerativerepeater which is designed to receive the distorted signal elements andin response thereto regenerate and retransmit signal elements whichcorrespond exactly with the original signal element in shape andduration. IThe regenerative repeater identities l the nature of eachsignal element, generally by sensing the middle portion of the signalelement, and then transmits a signal element of corresponding nature andof standard length by means of a mechanically or electrically controlledtim- .ing device which restores each signal element to its standardduration. It is particularly pointed out that only a single regenerativerepeater unit is required to serve any concentravtion group ofinterconnected lines or loops in a multiway regenerative repeater at aparticular city. Numbers of such groups located in diierent citiesremote from each other are ordinarily interconnected together through anindividual regenerative repeater for each group. Although presentlyknown multiway regenerative repeaters operate generally satisfactorily,it has been found that they are subject to a diliiculty which results inthe occasional loss of a short message when two or more parties atremote points seize the line approximately simultaneously. The reasonfor this is that spacing signals cannot pass each other over the system.

lt is a more specific object of this invention 2 to prevent the loss ofshort messages on multigroup networks interconnected through multiwayrepeaters.

The loss of short messages on multigroup networks is prevented throughthe modication of the presently known multiway repeater circuits toprovide what will be termed hereinafter a double-space lay-pass feature.The double-space lay-pass feature permits space signals in effect topass each other at regenerative points and minimizes simultaneoussending by assuring rapid and positive mutilation of local copy whichserves as an indication of the attempted simultaneous transmission.

A feature of the invention is a double-space by-pass arrangementincorporated into a multiway regenerative repeater.

A further feature of the invention is an arrangement whereby themultiway regenerative repeater and the double-space by-pass circuit maybeA readily interconnected or disconnected as required bythe repeaterattendant depending on the needs of particular networks as they areestablished or modied thus eiecting a saving in the number ofdouble-space by-pass units required.

A further feature of the invention is the modication of the directionalrepeater so that it can respond to a spacing or break signal receivedfrom a connected line repeater during the interval while a spacingsignal is being transmitted from the directional repeater toward theline repeater.

A further feature of the invention is the provision of an arrangement inthe directional repeat'er' so that it can discriminate between a spacingor break signal received from a line repeater and a spacing or breaksignal received from a subscriber loop during the interval while thedirectional repeater is transmitting a spacing signal toward the linerepeater or the subscriber loop and which enables the directionalrepeater to respond to the spacing or break signal received from theline repeater and remain unresponsive to the spacing or break signalreceived from the subscriber loop under such conditions.

These and other features of the invention may be understood fromreference to the associated drawing, disclosing a preferred embodimentof the invention, in which:

Fig. 1 shows three directional repeaters connected individually to threetelegraph channels;

Fig. 2 Shows a regenerative repeater, a doublespace by-#pass unit and ahub through which the directional repeaters of Fig. 1 are interconnectedThere has heretofore been a diiiculty encounto Fig. 2; and teled in theoperation of multiway regenerative Fig. 3 shows a typical half-duplexmulitway repeater networks in that it was impossible for regenerativerepeater network formed by intera spacing signal generated in oneconcentration connecting subscriber loops and telegraph lines 5 group ata particular city to pass another spacing through three Figs. 1 and 2 inthree diierent. signal generated in a concentration group at an- Citiesother city. `.Under-such circumstances short messages were 'frequentlylost. lThe double-space by- GENERAL DESCRIPTION OF THE SYSTFM pass unitshown at the lower part of Fig. 2 now Refer t Figsl and 2- Beforepfoceedmg Wlt'h l0 prevents this from happening. By means of the adetailed description, a general description of the doublepace .by pasunit, if for instance direc- Operation `O the System Will be 'given-F1g5 '-1 tional repeater No. 1 is transmitting a spacing and 2 wheninterconnected with Fig. 1 at the Signal and Simultaneously a spacingsignal is left of Fig. 2 exemplify the circuits constituting a -recevedfrom direc-tional repeater No. 2 the particular concentration grouptogether with Vits doub1e spa gbygpass unit Wm identify the Conc-[1regenerative repeater and tS doube'spac? by* tion. The vdouble-spaceby-pass unit will prolong DESS unit in a telegraphtest I@02H11 atarpar'tllllar the `spacing interval for a measured period whencity.Other corresponding circuits Such as Flg- 1 ever two spacing signals arereceived simultaneand Fie. 2 will be located et distant cities and ouslyor in suoli e time relation that their interinterconnected into ane'tWOrk by e Single Pel?- 20 vals overlap- When such a condition occursthe graph channelinterconnectingthe groups as 1nd1- doub1e spaceb5/:pass inuit willv impress a prt)- cated in Fig. 3. Extending from thelefthand longed spacing signal onthe entire system. The margin 0f Fig. 1are three conductors. Each 0f spacing interval will .be .prolongedsufciently so these three 'conductors may connect externally tiiatit hastime 4to reach tnefmos't remote Lfacility t0 a telegraph line repeater,not Shown, 'and 25 connected into the system. As long assimultanethrough the repeater to a telegraph-channel eX- oustransmission continues, long spacing .signals tending t0 e dstttrltrCiti 01' the Conductor may will be .generated and impressedon thesystem 'by' connect to a local subscriber telegraph loop or a the doub1espace by pass unit The eect of this particular conductor may 'connect t0'beth a 1in? is to mutilat'e thersignal'e which .are transmittedrepeater and a loop. Each telegraph Channel 1S 3o and lto 'insure thatthey are received by ever-y interconnected through -an individualdirectional facility Connect-ed into img system. The message repeatermarked directional repeater N0 -1I `2 and which isreceivedfat eachstation will definitely be 3. in Fie. 1 t0 'c hub circuit Shown et theleft 0f mutilated and will continue to -be 'mutilated es Fig. 2. Thethree directional repeaters-are served long tas .simultaneoustransmission Continues, bye. single vregenerative `repeater unit chownat a5 This serves as an Vindication that `more than one the tOlJ A0f Fg-A2 and by e double-Space hr-Dass transmitter is :being operated'simultaneously on unit shown at the bottom yof Fig. 2. Although thesystem. 'Onfobservi'ng-the condition, the parthere are but threedirectional repeaters shown-in ties :who 'are:transmitting:simultaneously will stop Fig. v1, it is understood thatrany num-ber 0f re* and'transinitting.mayibe'resumed by'one party.

peeters up to 'ten may be interconnected in a 40 on its regenerative'side each directional rehv particular Concentration group. If vmorethan ten peater is 'wired 'to 4'iii/e individual hub circuits,l

arerto vbe interconnected, two hub groups are shown'atithe fleftof-Figj2. The regenerator and interconnected. Signals may be receivedfrom the double-space thy-pass Aunit are connected to cerfacilityconnected to directional repeater No. 1 tain of these hubs through aspecial jack circuit over its corresponding'telegraph-'channelend imf45shown alsoat the left 'of Fig. 2. The jack circuit pressed 0n theregenerative repeater. The regenprovides 4for 'substitutions ofregenerators and erative repeater 'will reshape and Tetme 'theSigdouble-space Aby-pa'ss 'units by patching.

nal and transmit the signal simultaneously to p Y directional repeaterNo. 2 and directional repeater DETAILEDDESCRIPTION OF OPERATION 0FSYSTEM No'. 3 and through them over -the telegraph chan- 60 R 'e'at'ern' e't nels individual -to each vto remote cities where the ep a d nwork when idle channels Vare extended through :individual "direc-Each-of fthe relays .shown Ain Figs. 1 and 2 extional repeaters to thehubs of other concentracept power supply relay 92 in Fig. 2 is a hightion groups vor to the connected subscriber VVVloop. speed ipolar relay,The `circuitper Figs. 1 and 2 Thus, any one of the-telegraphriacilities:connected is "shown for the :idle conditionwhich'is the .Same to directional repeater '1, 2 or 3, "or'others ifthere as for the marking condition. The various relays are more in thegroup, may transmit through the in Fig. 1 and Fig. i2 will bein vthe.condition shown single one-way regenerative-repeaterunit tovall of forreasons which will become apparent hereinthe other channelsinterconnectedto a particular after. When the network :is idle receivingbreak group at a particular city, as well as to all of the "'60 relay YIand receiving relay 2 'associated with other groups at the remote citiesand through the directional rep-eater No. l are in the markingconregenerative repeaters at the remote cities to each dition as shown.The :corresponding relays in of the facilities connected Ainto thevarious groups directional vrepeater viNo. 2, :relays 20! and 22,

at'the remote cities. Y Y and rthe corresponding relays in directionalrei -Signals incoming to a'particular directional re- '65 peater No. 3,relays 30| :and 302, are also in the -peater connected to a 'particularchannel vof -a marking condition. The directional repeaters group ataparticular city vare impressed on kthe transmit polar Vsignals. towardthe distant end incoming circuit of Vthe single regenerativerefrombatteries whichs'may, for instance. be i130 peater unit'associatedwith the group and, after volts. The-directional repeaters transmitneutral regeneration, are impressed simultaneously by '70 signalsthrough a .hub circuit toward the regen-` theoutgoing circuit of thesingle regenerative erator repeater. The signals may, for instance,repeater unit on all of the other directional rebe negative 48 volts formarking and ground for lpeaters connected into the group except thespacing. The regenerative repeater terminates directional repeater fromwhich'the 'signal was on its incomngvside iin Ynegative 'L18-voltbattery received. and on its 'sending side 'connects vnegative" 48 voltsto the sending hub for marking and ground for spacing.

It will be assumed that the incoming signals were last received bydirectional repeater No. 1 from the incoming channel. Under thiscircumstance holding relay 3 will be in the spacing condition. Holdingrelays 203 and 303 in directional repeaters Nos. 2 and 3 will be in themarking condition. The sending relays Nos. 4, 204 and 304 in directionalrepeaters Nos. 1, 2 and 3 will be in the marking condition. Thereasonsvior this will be made apparent below. The detailed operation ofthe regenerative repeated in the upper portion of Fig. 2 is described indetail in Patent 2,105,173, Walter J. Zenner et al., January 11, 1938,and Patent 2,337,496, W. T. Rea, December 21, 1943. The descriptions ofthese patents are incorporated herein by reference as though fully setforth herein. Receiving relay 8| in the regenerative repeater will be inthe marking condition. The transmitting element I0| of the regeneratorunit will be in such position that contact |04 is closed.

Plug |32 will be withdrawn as indicated from jack 3|. Under thiscondition a circuit may be traced from battery through the winding ofrelay 92, contact 13, contact 10 and contact |33 to ground energizingrelay 92. The armatures of relay 92 will be actuated to close contacts94 and 95. With contacts 94 and 95 closed, power is supplied from powersource 93 to motor 90 so that the driving shaft associated with theregenerative repeater mechanism is turning continuously. A stop arm, notshown, engages a shoulder on cam 99 and prevents the driven shaft of theregenerator from rotating through friction clutch 91. The filament ofvacuum tube |23 is heated over a circuit which may be traced from groundthrough battery I i6, resistance II'I, resistance I 24, lament of tube|23 and resistance |22 to ground. Condenser |20 is charged to thepotential of battery I I6 over a circuit from ground through positivebattery IIB, resistance IIl, resistance IIS and Variable resistance IIBto the left-hand terminal of condenserY |20, the right-hand terminal ofwhich is connected through resistance I2| to.ground. The grid of tube|23 is connected through resistance |40 to the junction between theleft-hand terminal of condenser |20, left-hand terminal of variableresistance |I8 and spacing contact II5 of relay ||3 which at this timeis open. Current normally flows through vacuum tube |23 over a circuitwhich may be traced from ground through resistance |22, filament of tube|23, plate of tube f |23, winding of relay |25 and resistance |I`I togrounded positive battery. For this condition the armature of relay |25is actuated to the left to engage its contact |26.

With the various relays in the assumed condition, a circuit may betraced from positive battery I3. through resistance I4, marking contactII of transmitting relay 4, through inductance coil Sii and resistance3| in parallel to the apex of relay 2 where parallel branches areformed. One branch extends through the top winding of relay 2, topwinding of relay I, resistance 2| and variable resistance I9, whichconnects either to 'a line repeater and through the line repeater to amultiway regenerative repeater concentration group, such as that perFigs. 1 and 2 at a distant city as indicated in Fig. 3, or the variableresistance I9 may be connected to a subscriber loop circuit. In eithercase the connecting circuit iS terminated in negative and positivebattery of the same magnitude as batteries I3 and I5. Neg- ,ativebattery will be connected at the distant end tom winding of-relay I isshunted by resistance 24; From the right-handterminal of resistance I abranch extends'through resistance |44, and resistance |42 which isshunted by condenser |43 to the top terminal of resistance 23. Theseresistances and their connected battery constitute a potentiometernetwork which controls the magnitude of the currents owing in the bottomwinding of relays I and 2 which varies one from the other for differentconditions to be explained hereinafter. The effect of the current owingin the top winding of relays I and 2 for this condition tends to operatethe armatures of relays I and 2 toward the left to engage with theirrespective marking contacts 5 and 1, while the effect of the currentflowing in the bottom windings of relays I and 2 tends to actuate thearmatures of these relays toward their respective right-hand contacts 6and 8. For the marking condition the eifect of the current iiowingthrough the upper windings of relays and 2 is dominant over the effectof the current flowing in the bottom windings of relays I and 2 and thearmatures of relays I and 2 are maintained in engagement with theirrespective marking contacts 5 and 1.

Since contact 8 is open and ground from the armature of relay 26 istherefore not connected vto contact 8 and since the same conditionprevails at contacts 208 and 308 there is no ground connected throughconductors d5, 5i) or 55 to receiving hub 62. From hub 62 a circuit maybe traced through contact E5, contact 98, top winding of relay 8|,resistance 8l, resistance 85, which is shunted by condenser 8E, andnegative battery 84 to ground. For this condition therefore the topwinding of relay 8| is not energized. A circuit may be traced fromgrounded negative battery 84, through resistance 88 and the bottomwinding of relay 8| to ground. The effect of current flowing in itsbottom winding maintains the armature of relay 8| in engagement with itsmarking contact 82. For this condition a circuit may be traced fromgrounded battery 89, through resistance 90, armature and contact 82 ofrelay 8| and the winding of the regenerative receiving magnet 9| toground, energizing magnet 9 I. When the magnet 9| is energized whileawaiting the reception of a train of signal elements, the driven shaftof the lregenerative repeater mechanism is prevented from rotating inthe manner explained in the foregoing. Sending contact |04 of theregenerative repeater is closed for this condition and a circuit rnay betraced from grounded negative battery |05, through resistance |05 whichis shunted by condenser |08, resistance |01, contact |04, conductor |09,contact B'I, contact 64 to sending hub 6I, where parallel branches areformed. In the case of directional repeater No. 1, branch 42 extendsthrough the top winding of relay 4, resistance 4I and resistance 39shunted by condenser 40 to contact I0 of relay 3, which is open since asexplained heretofore, the armature of relay 3 is in engagement with itsspacing contact 9. VIn the case of directional repeater No. 2 theparallel neonato.

flinch-extends. through conductor 41, 'top Lvrinding of relay 204,resistance 24|., .resistance l238, 'wl'xich-is-shunted by condenser 240,contact 2&0, whichris closed, .and the armature of relay 2.03110negative battery 229-. In the case of' directional repeater No. 3 theparallel branch extends through yconductor-152, top winding of relay304, resi-stance 34|, resistance 339, which is shunted by condenserV340,1eontact 310, which ciosed, and the armature of relay 303 tonegative batteryl 329. .No-current therefore flows in the top windingsof any ofthe sending relays in directional repeaters No. 1, 2 or 3. "Thearmatures of each of theserelays is maintained `in engagement with itsrespective marking contact due to the eifect of current owing vthroughits bottom `winding in each instance. In thecase of relay 4 the circuitmay be traced `from ground through resistance 38 to parallel branches.One branch extends through resistance 31 and negative battery 36 toground. Theother branch extends through the bottom kwinding of relay 4,resistance li8 and negative battery l1' to ground. The-correspondingcircuit for relay 204 maybe traced-from ground through resistance 238 topar- 'a'llel'branches One branch extends through resistance `2311 tonegative battery 236. The other branch extends through the bottomwinding of relay V'2M andresistance 218 to negative battery 21T. In thecase of relay 304 the circuit extends from ground through resistance 338to parallel branches. One branch extends through resistance 33T `tonegative vbattery 335. The other lextends through the bottom winding ofrea-y 304, resistance 3 i8 and negative battery 3 I1 to ground. Acircuit may be traced from negative battery 29` through the armaturespacing contact 9 and bottom Winding of relay 3, resistance 32, which isshunted by condenser 33, and conductor 44 Ato 'holdinghub 58 which4extends through the holding hub resistance 51 to ground.` The `current,flowing through the bottom winding .of relay 3 may, .for instance, Ybe.025 ampere vfor this condition and its effect is tending to actuate thearmature of relay 3 towards its spacing contact 9. `With the armature ofrelay 2in engagement with contact 1 this effect is opposed by the'euectlof current in the upper Winding of relay 3 which is tending to actuatethe armature of relay 3 towards its marking contact l0. The magnitude ofthe current in the upper Winding may, Vfor instance, be .020 ampere andthe armature of relay 3 will be maintained, as has vbeen mentioned, .inengagement with Vits spacing contact No.` 9. The circuit which controlsthe flow of current through the upper winding of relay 3 is in the formof a double potentiometer. 'The circuit may be vtraced from negativebattery 29 to the junction between resistances 26 Vand 28.` From thisjunction one branch of the circuit extends through resistance 28 to thejunction of second parallel branches. One second branch vextends throughresistance 21 to ground. rIrhe other second branch extends through thetop winding of relay 3 to the lower .terminal of resistance 26, fromwhich point the circuit extends to marking contact 1 of receiving relay2. When the armature of receiving relay 2 is. in engagement with litsmarking contact .1 the .circuit 'is extended through the armature ofrelay 2 to ground. The magnitudes of the resistances and of the batteryforming the Vpotentiome- .ter have been so chosen that the direction ofthe idow ci current through the top winding of relay 3is reversed as thearmature of relay y2 engages with---and diseneases from contact 1. .re-

verset is almost instantaneous because it is effected simply by theengagement and separation of thearmature of relay 2- Withand fromcontact 1. In. .thecese of relays 2ll3l and 303, since their respective'armatures are not in engagement with their respective spacing contacts229' and 303, no `current is owngthrough the bottom windings of .theserelays. The potentiometer circuit con.- nectedto thetop windings ofrelays 203 and 303 is identical vin its arrangement with that connectedto. the v'top winding of relay 3. The effect of the :currentowingthrough the top windings `of re- -lays 203and3l3 is in eachinstance in a direction to maintain the armatures of these relays inengagement vwith theirrespective marking contacts 210 and 3|'0.

'Transmission toward the reycnerator It. will now -be assumed that thelineV associated with :directional Vrepeater No. 2 starts to send towardthe regenerator. It will be assumed that thesignals which are receivedare. the well-known trains of start-stop permutation code signalscomprising a. start elementv which is always a spacing signal -element,five. permutation code ycharacter forming elements which may be markingor Vspacing signal elements -i-n any combination depending upon theparticular character and a stop element which is always a marking signalelement.

The first signa-l element which .is received is a spacing signal elementand will interrupt the flow .of current in .the upper windings of relays2.0i and 202 and thereby vcause these relays to operate to .theirrespectiveA spacing contacts 206 and .203 under the influence loicurrent in their lower windings. Closure of contactZB connects groundthrough conductor v5l]v to receiving hub S2 from which point -thecircuit has. been traced through the top winding of relay 8l. As aresult of. this, the. armature 4vo relay 3l will be actuated to engageits. open A.spacing Contact 83.. This in turn will -deenergizeregenerator receive magnet 9| which will remove the stop arm (not shown)from engagement with a. raised surface on the periphery of cam 99 andpermit cams 98 and 99 to rotate through-one complete revolution duringwhich interval, in .addition to the start pulse, the five characterorlning .elementsand the stop sig- .nal .element of. which each signaltrain is confstitutedwill be received in sequence from directionalrepeater 2. The armatures of relays 29.! and 202 `operate in unisonwhile relay 204 remains in the. marking condition. The instant that theyarmature of relay 202 breaks from its marking 4contact 2&1 and beforethe armature .of relay 202 Ahas .completed its travel to engage.itsfspacing contact 208, the. direction of the How of current in thetop winding of relay 263 will m rbe reversed and the armature of relay2&3. will l'l5 holding hub resistance 5l.

be .actuated to. engage with its spacing contact 20.05. When thearmature of relay 263 engages withits spacing .2&3 a circuit may betraced from negative battery 2.2.9, through the armature spacing contact20S and bottom winding of relay 203, lresistance v232 Vwhich 'is.shunted by condenser 23.3,', conductor 4.9., holding hub 58 and throughhub resistance '5T to ground. Since the armature of relay '3 is stili'in engagement with its spacing ,contact 3, since it is assumed that theexternal 4channel cormected to directional repeater l was thelasttotransmit toward the regenerator, there .are twoifparallel branches,namely, the branches connected to conductors 44 and 49, connected to The.magnitude lof thecurrent owing; in the bottom winding 4of relay 3 andinthe `bottom Winding of relay 203 may be, for instance, approximately.015 ampere for this'- condition.. `lrThis current will be insuil'-cient to maintain the armature of relay 3 in engagement 'with itsspacing Contact for this condition since, Aas Yexplained in theforegoing, it is opposed by a current of approximately .020' am.- perein the, top winding-of relay 3 which is tending to actuatethe armatureof relay 3 toward its marking contact II0.'-""The armature of relay 3Willtherefore be actuated to close its marking contact l0.. the case` ofrelay 203 the effect o f Ithe- 'current in .both its top and bottomwindings at this timefis tending to lmaintain the armature frel'ay 203mengagement with its spacing-'contact andfthefarrnature of relay 203 willremain" in engagement with its' spacing contact. Thelinstan't rthat theVarmature of relay 3- disengages -rOmits spacingcontaict3- one of theparallel branches Vcornected'to vholding hubl resistance5'l,=.narnely,'. the --branch4 through conductor 44 .in directionalrepeater No.V 1, will be disconnected and the current through the bottomvlinding of relay .203 will'risf. to its full value of .025 ampere in aspacingfdirection and this will be sufcient tohold the armature of relay203 in engagementhwith its spacing contact 239 after the -cu'rrent'in-its upper winding has been reversed to .020 ampere in a markingdirection by reception of marking pulsesv from the line repeaterassociated with repeater No. 2 during communicationandthe consequentclosing .of contact T.

l .'From the foregoing 4will be .apparentA that only one of. the holdingrelays, 3, 203, or 303 in the various `directional repeaters can belocked in the spacing condition by current ilow through its bottomwinding to the holding hub resistance 57 at any one time.

, It is veryimpor'tant that a holding relay such as 3, 2.03 or'1333,which has been previously locked tofits spacing Contact .while it hasbeen receiving communicationlfrom its external channel or during the.lwaiting interval thereafter, be very quickly released, when a secondchannel starts to transmit and the corresponding holding relay in thesecond channi is operated to its spacing contact by c urrent in itsupper winding, in order tov arrange the. circuit ofthe holding relaywhich has been. formerly locked to spacing so that the directionalrepeater with which itis associated is in a conditiomto transmit, beforethe rst regenerated signalelement from' the newly transmitting channelis -receivedjr'om the regenerative repeaten Mention .waslinade of thedouble potentiometer arrangement .connectedto the top windinglof each ofthe holding relays 3, 203 and 303andf-of the fact that. ,current throughthe top,.,ivinding of .these relays was reversed instantly 'upon the.engagementor disengagement of the corresponding receiving relay 2, 202,or 302 rfithor from its respective marking contact fl, gill 'or ,301. Itis vthe function of .the condenser such as ".33,7233 or 333, shuntingresistance 32, 232 or.. 2,32 l"to speed up the release of a relay whichhas beenlockedin the spacing condition. ".ll'iev effect of theconnectionof the condenser in each of these circuits 1ls-to produce aninstantaneous surge of cur'rentin the marking direction or a magnitudesuiiicient to release the 'held relay, such as relay. 3 in thedirectional repeater which last transmitted toward the` regenerator.

-It has been; assumed thatV the directional repeater N0.- 1 'was thelastftefrsceive fromts external channel and that the armature ofitsrelay 3 is in the spacing condition when a signal is rst received bydirectional repeater 2. If the start pulse had been received from thelcircuit associated with directional repeater No. 3, relay 3 ofdirectional repeater No. l would have been operated to marking whenrelay 303 of directional repeater 3 Was operated toward spacing in themanner described for directional repeater No. 2. The start pulse in thiscase would have been transmitted over conductor 55 and into theregenerative repeater through hub 62. If the start pulse had beenreceived from the line repeater associated with directional repeater No.1 the holding relay 3 of directional repeater 1 would have remained inthe spacing condition and re' ceiving relay 2 would have transmitted thestart pulse through hub 62 to the regenerative repeater. The holdingrelay such as 3, 203 or 303 in anydie rectional repeater is thereforeoperated to spacing only when its directional repeater starts tosendtoward the regenerator and the holding relay remains locked in thespacing position as long as transmission continues to be received fromthe line associated'with this particular regenerative repeater. and,after transmission in this particular direction ceases, the armature ofthe holding relay will remain in the spacing condition until it isreleased by the operation of a holding relay in another directionalrepeater which startsY to send toward the regenerator.

The directional repeater which is sending to ward the regenerator willcontinue to transmit through hub 62 on an inverse neutralbasisconnecting ground to the hub through its respective receiving relayfor spacing and removing ground from the hub for the marking condition.fl

Reception from the regenerator The initial start pulse transmittedtoward the regenerator by the receiving relay 202 of directionalrepeater No. 2 as described in the foregoing will be regenerated andafter a momentary delay will be repeated by the regenerator to sendinghub 6I. The regenerator grounds sending hub 6| in repeating the startpulses by positioning the right-hand end of transmitting lever llll inits lower position in response to the deenergization of magnet 9|, whichcloses contact |03- connecting ground through contacts 6'! and 54 to hub5I. Current ilows from ground on hub 6| through the top windings of alltransmitting relays such as 4 and 304 to negative 48-volt battery suchas 29 and 329 except through transmitting relay 204 associated withdirectional repeater No. 2 which is transmitting toward the regenerator.Current is prevented from flowing through the top winding of relay 204because the associated holding relay 203 is in the spacing condition andthere is no closed path therefore through the top winding. of relay 204,contact 2|() and the armature of holding relay 203 to negative LlS-voltbattery 229. Transmitting relay 204 of directional repeater No. 2 thusremains in the marking condition under the influence of current in itslower winding. The transmitting relays of all other directionalrepeaters are operated to the spacing condition by the eiiect of currentin their upper windings because the path through the armature of each ofthe holding relays such as 3 and 303 is closed through to negativebattery such as 29 and 329 in each instance. The start pulse willtherefore be repeated to all line and loop facilities which areassociated with directional repeaters other than directional repeaterNo. 2 which is sending associated linesind l tei-posing the stop` arm inthe path 'of a raised i surface of cam 99. Then the cycle will berepeated for the next character.

When the direction of transmission changes the holding relay ofdirectional repeater No. `Zvvl'iitli has been transmitting toward theregenerator 'is operated to the marking condition and the holdingirelayof the directional repeater which is beginning to transmit toward theregenerator is locked in the spacingcond-ition before the start pulse isretransmittedby the regenerator;

Break:r feature First the manner in which `the multiway regenerativerepeater functions-for the transmission of 'a vbreak sign-aivvhen thedouble-space bv-riass circuit is disconnected will 'be described. Let itbe assumed that contacts 16 and 'I1 are opened disconnecting thedouble-space lav-pass circuit.

A. While directional repeater-No. 2 is' transmitting toward theregenerator let it beassumed that 'the line associated with directionalrepeater No. 1 trlesrto break by sending va spacing pulse of severalkseconds duration by connecting positive battery to the channelincomingl to `directional repeater No. 1. If the spacing pulse isreceived when the transmitting relay A4 of directional repeater No. l isin the spacing condition receiving relay 2 of directional repeater 1will remainin the yrnarl'ring condition because the magnitude of theholding current in the lower winding of relay 2 exceeds the vmagnitudeof the spacing current in the upper winding of relay '2. It. isimportant to observe that with this arrangement, that is with thedouble-space by-pass circuit disconnected, a break signal is noteffective while a spacing signal is being transmitted against it `Assoon as the transmitting `relay 4 operates to marking, however, inresponse to the next marking signal element from theA regenerator,thecurrent in the lower winding of relay 2 reverses to the spacingdirection and since there is now no current in the upper winding ofrelay 2f, relay 2 operates to the spacing condition iollowed by itsassociated holding relay 3.' Operation of holding relay 3,to the spacingcondition will serve to prevent reoperation of transmitting relay 4 tothe spacing condition and thus insure passage of the break signalbyreinoval ofv-negativeiB-volt battery from the operating circuit ofrelay 4 at open contact I0. This will also cause the holding relay 203of directional repeater No. 2 to operate to its marking condition in themanner described in the foregoing. Operation of receiving relay 2 ofdirectional repeater No. 1 to the spacing condition connects groundthrough conductor 45 to receiving hub 62 and transmits the break signalto the regenerator.

After a momentary delay the break signal is repeated by the regeneratorwhich connects ground to sending -hub 6|- and causes the transmittingrelays 204 `and 304 of directional repeaters Nos. 2 and 3, respectively,toY operate to the spacing condition and repeat the break signal totheir nais from theirfsocated'iiwminmltamonsly the directional-nepeeterfwhiclrfto receive. a spacing'signar,aft'erV repeater has.changed back to maxtingfwill gn control of the lhoitlngfrelay will beinthespaeingccndition.

` .DOUBLE-Srsclzfrfrssffmm As mentionedfabove-the' ivy-pass circuit isshownl at the/lowetrightof Fig. 2. It ,is connected todouble-spaceireceiving 5l fand doubie-space'scndng hub IQ hymns oijl'mb.jack 'l5 and by-passjack Hfwhieirperniit-substitution ofone-double-space-by-pass fcr'another by patching.` The by-passjcircuitprovides a form of break feature since itspurpose is to notify aninterconnected "teierype'writer numana particularlya sending teltymrterlstation that more than oneteletypewrterstationon the samt half-duplexVnetwork is sending simultaneously.

The lay-pass -crcitneednot ,aiways be provided andwithout. it themultiwayregenerative repeater network is1 capa-ble x offbreskingi1-Liliev normal manner described in :the oregoingc'ne' by-pass circuitis' particularly whmziznumber of ,multiwayv regenerative n:repeaterarrangementsr are included -i-n alarg'emultlsiation teletiming circuitwhich protratta-ihn Spacing, signal vtfor an extended interva when twoyare received substantially simulta neously to insure propagation tothemost rcmote stationpcnnccted v'to the mostremote group inthe-,netwerkY'urther it makes it possible tofreceivnf-afspacefthmugh a directionalrepeater which, .at the 'is transmitting a spacereceived*from'tnegegenerator. Thus no signals vcan be, lostf The'eifectfof the operation of the'douple-space'bspm circuit isv tocontinue to transmityicng spacing signals while simultaneoustransmission which..v mutilates the signals received Vbygall.stationslnterconnccted'-ithrcrlfxgh the network as'anebctveindication' UfhdCOIldiiOn.

Y Duringnormaimmmisien-mzaeireaimai repeater to theregenerator-thereceivingv breakr` relay in the particular directions?repeater which is transmitting towardthe regmeratbr such-*asl receiving'breakl relayV if inV directionai repeater' No. i respondsftothc'signals incoming'fromthe line repeatercrSubScribcrsiGOni'JEach-timethe .receiving break relay sncliasfrciayieperatesA to,

yspacing it connects erigir time ,sani

as grounded high resistance l!" a' ccn doctor such as conductor 4l 1to1tireffddubie-spml'e by-pass receiving hub 59'.' Prom; hiib like circuitextends throughcontact i-fof lia'nd contact Bil of jack 18, top windingof rciaysiitand :i i!

'in series and resistanceiila tornositiyebatterly HS. This causesyspacingcurrent Avv'liich may;

` for instance, be approximateiy ,'.Umgampere to rectional repeaterswill be operated to spacing and both relays will connect highresistances, such as 22 and 222, in parallel between ground and hub 59.This will cause a spacing current which may, for instance, beapproximately .024 ampere to iiow in the upper windings of relays and||3 of the by-pass circuit and this will cause relays and |i3 to operateto spacing. The operation of relay il@ to its spacing contact ||2 willestablish a circuit from ground through contact 2, Contact 19 andcontact 16 to the double-space by-pass sending hub B0. From hub 6|!circuits extend through the bottom windings of each of the transmittingrelays, such as relays 2M and 3M, of the various directional repeaters.In response to this each of the trans-v mitting relays, such as 5, 234and 304, will be reversed to spacing which will transmit a space orbreak signal out to all interconnected lines and loops.

In order to insure that the break signal reaches all of the stations onthe network it is desirable that this spacing or break signal betransmitted for an appreciable period and since relays Hi) and I3 willremain in the spacing condition only g momentarily during the intervalwhile -both in coming space signals persist simultaneously theprotraction of the spacing signal must be accomplished by special means.This is accomplished in the following manner.

When relay ||3 closes its spacing contact H5 ground is connected to theleft-hand plate oi condenser l2|l in the by-pass circuit which causescondenser |26 to be discharged. This reduces the grid potential of tube|23 sufficiently to stop the flow of plate current in tube |23 whichplate current normally flows through the winding of relay |25 topositive 13D-volt battery Ht. Relay |25 therefore operates under theiniiuence of its mechanical bias spring so as to close contact |2'i.This establishes a circuit from ground through contact |21, contact i9and Contact 1B to hub B0, supplementing the ground that initially wasconnected to hub tu through contact ||2 of relay lill. When relays ||iland ||3 return to the marking condition at the end of the doublespaceinterval relay Il removes ground froml hub til and relay H3 removesground from the left-hand plate of condenser |29 which begins to chargeover a circuit which has heretofore been traced. i

After a predetermined interval of delay, which" can be adjusted betweenthe limits of 50 and 500 milliseconds by means of variable resistanceIIB, the left-hand plate of condenser |253 and the grid of tube |23reach a potential sufficiently high toV cause the normal plate currentto be reestablishedj in tube |23. At this moment relay |25 opens contact|21 and closes contact |25 removing ground from hub El) and therebyrestoring the current in the lower winding of the transmitting relays,such as d, 2M and 304, of all directional repeaters to the markingdirection. If all lines and loops are in the marking condition towardtheir respective directional repeaters the armatures of all transmittingrelays such as relays 4, 204 and 304 will be operated to close theirmarking contacts. However, if one line or loop is still in the spacingcondition all transmitting relays will remain inv the spacing conditionexcept that of the directional repeater which is transmitting a spacingsignal toward the regenerator which transmitting relay will be in themarking condition. The length of time which the spacing or break pulseshould be transmitted should be slightly longer than the propagationtime of a signal to the most remote station on the network.

Full-duplex loop feature The directional repeater is so designed thatwhen its transmitting relay such as relay l is in the spacing condition,reception of a spacing signal from a line repeater to which it isconnected will cause its associated receiving break relay such as relayto operate to the spacing condition. This enables the receiving breakrelay of the directional repeater to respond to spacing signals from theline repeater regardless of the position of the sending relay such asrelay 4 of the directional repeater. This is achieved by means of thepotentiometer circuit connected to the bottom windings of the receivingand receiving break relays in each directional repeater. Without thisfeature a spacing signal from a line repeater on reaching a directionalrepeater, the sending relay of which happened to be in the spacingcondition, would fail to operate the receiving break relay to spacing.Thus, unless two spacing signals arrived almost simultaneously from thetwo lines involved, one would lock the other out. The double-spaceby-pass circuit would not respond in the manner desired without thisfeature which is called the full-duplex loop feature.

When a space signal from a line repeater is received by a directionalrepeater the sending relay of which is in the spacing condition, thereceiving break relay operates to spacing due to a spacing current whichmay, for instance, be approximately .0585 ampere in its upper winding,which opposes a marking current which may, for instance, beapproximately .0465 ampere in its lower winding. Under Such conditionthe associated receiving relay remains on marking due to a markingcurrent which may, for instance, be approximately .070 ampere in itslower winding which opposes a spacing current, which may, for instance,be approximately .0585 ampere in its upper winding. It should be noted,however, that the receiving break relay and the receiving relay in adirectional repeater both remain in the marking condition when theassociated transmitting relay is transmitting a spacing signal and aspacing signal is received from a subscriber loop instead of from a linerepeater. The break signal received from a subscriber loop opens thepath through the top winding of the receiving and receiving breakrelays, such as relays and 2 so that, if it is received whiletransmitting relay 4 is on spacing, the armature of both relays 5 and 2will be maintained on their respective marking contacts under theinfluence of the cur.- rent in their bottom windings which will be in amarking direction for this condition.

Goodnight feature When it is desirable -to temporarily remove a multiwayregenerative repeater arrangement from service either for the periodicgoodnight or for more or less extended intervals it may be 05 done byinserting plug |32, which has its tip conductor connected to its sleeveconductor, in jack ISI, at the test board. This opens the path4 whichwas formerly traced through the winding of relay 92, opening contacts 94and 95 and dis- 70 connecting the power source 93 from motor 96.

The insertion of plug |32 in jack |31 establishesbranches which extendinto each directional re 15y peater'such-asbranches 42, 41 and 52. Thisoperates each of the transmitting relays, such as relays 4, 254 and 384,to the spacing condition. The transmitting relays are maintained in thiscondition as a goodnight signal which is transmitted to all of theinterconnected lines and loops in the network.

Substitution of a regenerative repeater A spare regenerative repeatermay be substituted for the regularly assigned unit in the followingmanner.

` One end of a two-conductor tip sleeve patching cord is connected tothe regenerator jack E' in Fig. 2 or an idle unit. This disconnects theregenerative repeater regularly assigned to the: idle unitby openingcontacts 6l and 68. The opposite end of the tip sleeve patching cord maybe connected to jack 63 of the Fig. 2 in which the substitution is to bemade. This disconnects the regularly assigned regenerative repeater byopening contacts 64 and 55 and connects the idle` unit through the tipsleeve conductors of the jacks and the patching cord.

A similar patch is made from motor control Tack 'l2 associated with theidle unit to hub B jack B9 of the assigned unit to provide goodnightcontrol.

, Double-space by-pass circuit substitution A double-space by-passcircuit .may be substituted for the regularly assigned ley-pass circuitin the following manner.

One end of a two-conductor tip sleeve patching cord is connected to ajack such as jack 18 of an idle double-space by-pass unit. Thisdisconnects t'he idle double-space by-pass unit from the concentrationgroup to which it is regularly assigned by opening the contactscorresponding The opposite end of the patching to i9 and 89. cord isconnected to the double-space by-pass hub jack 'l5 in the concentrationgroup in which the substitution is to be made. This disconnects theregularly assigned double-space bypass circuit from its concentrationgroup by opening contacts '.16 and Tl and connects the idle doublespaceby-pass circuit through the tip sleeve patching cord and the tip andsleeve of jack 'I5 to the sending and receiving double-space bypass hubs59 and 5!! respectively.

What is claimed is:

1. A half-duplex inultiway regenerative telegraph repeater systemcomprising more than two individual telegraph repeaters interconnectedthrough hubs to a single one-way regenerative repeater unit, said systemincluding means whereby but one of said individual repeaters mayeffectively transmit through said regenerative repeater to all or theothers of said individual repeaters simultaneously through said hubs atany one time, and means in said system for effectively indicating, atremote stations connected to said multiway repeaters, a conditionwhereunder more than one of said individual repeaters attempt totransmit at any one 4time to said other individual repeaters, saidlatter means comprising instrumentalities for transmitting signals ofprotracted duration, substantially longer than the duration of normalsignals, so as to insure reception at said remote stations.

- 2. A half-duplex multiway regenerative telegraph repeater comprisingmore than two individual telegraph repeaters connected through a sendingand receiving hub to a single one-way telegraph. channel connected toany one of said,

individual telegraph repeaters, through said re ceiving hub to saidregenerative repeater at a nrst time, means responsive to the receptionof said signals from said individual repeater by said regenerativerepeater for transmitting regenerated telegraph signals irom saidregenerative repeater through said sending hub, through all of theothers of said individual repeaters to telegraph channels connected tosaid other telegraph repeaters simultaneously and through said channelsto remote stations, means connected to said individual repeaters foridentifying a condition whereunder more than one of said individualrepeaters attempt to transmit signals into said single regenerativerepeater at said rst time, and means for eii'ectively indicating theattempted simultaneous transmission through said regenerative repeaterto said remote Stations, said latter means comprising instrumen.-Vtalities for transmitting signals of protracted duration, substantiallylonger than the duration of normal signals, so as to insure receptionat.

said remote stations.

3. A half-duplex multiway regenerative telegraph repeater comprisingmore than two individual telegraph repeaters connected through a singleone-way regenerative repeater unit, means for transmitting telegraphsignals from any one of said individual repeaters through said singleregenerative repeater Aunit to all of the others of said individualrepeaters simultaneously,

means connected to said individual repeaters forr identifying telegraphsignals incoming from moreA than one of said individual repeaterssimultae neously toward said regenerative repeater, and means connectedto said individual repeaters responsive to the reception of saidsimultaneous signals by said individual repeaters for transmitting acharacteristic protracted signal to ef-v fectively indicate thecondition at remotel stations connected to said multiway repeater, saidprotracted signal of substantially longer duration than a normal signal.

4. In a telegraph system, a half-duplex mu1tiway regenerative repeaternetwork comprising a plurality of half-duplex multiway regenerativerepeater groups, each of said groups interconnectedby a telegraphchannel to another of said groups, at least three individual telegraphrepeaters in each of said groups, each of said individual repeaters in aparticular group interconnected together through an individual hubcircuit for each of said groups to a single one-Way regenerativerepeater unit, means in said system responsive to the transmission oftelegraph signals through any of said directional repeaters in aparticular group into the corresponding regenerative repeater fortransmitting regenerated telegraph signals through all other directionalrepeaters forming part of the same group simultaneously, means in saidsystem for propagating said regenerated signals through said channelsvconnected to said other directional repeaters to each other groupforming part of said network, means including said regenerativerepeaters: in said other groups for again regenerating said signals asthey are propagated through each of said other groups, a double-space'oy-pass circuit' connected to a particular one of said groups, meansconnected to said by-pass circuit for simultaneously receiving twospacing signal elements" generated in two groups of said network 17different from said particular one group and means connected to saidby-pass circuit for imposing a protracted condition on said system inresponse to said simultaneous reception.

5. In a telegraph system, a rst, second and third half-duplex multiwayregenerative telegraph repeater group, each of said groups comprising atleast three individual telegraph repeaters interconnected through anindividual hub circuit to a single one-way regenerative telegraphrepeater unit individual to each of said groups, a rst telegraph channelinterconnecting an individual repeater in said iirst group With a firstindividual repeater in said second group, a second telegraph channelinterconnecting a second individual repeater in said second group withan individual repeater in said third group, means in said systemresponsive to a telegraph signal received by any of said individualrepeaters in any of said groups for transmitting regenerated telegraphsignals to all other individual repeaters in each of said groups, adoublespace by-pass circuit connected to said second group, and means insaid by-pass circuit for effectively passing through said second group aspacing signal generated in said third group While a spacing signalgenerated in said first group is passing through said second group.

6. In a telegraph system, a multiway regenerative repeater group, adouble space by-pass circuit connected to said group, and means in saidgroup responsive to the operation of said by-pass circuit for eiectivelytransmitting a characteristic signal indicating the simultaneousreception of two spacing signals in said group.

7. A multiway direct current half-duplex regenerative repeater groupcomprising a first directional repeater, a second directional repeater,and a single one-Way regenerative repeater unit interconnected -througha hub circuit, means in said rst directional repeater for receiving aspacing signal and impressing said spacing signal through saidregenerative unit on said second directional repeater in a rstdirection, means in said second directional repeater for receiving asecond spacing signal incoming to said second directional repeater froma second direction, while said first spacing signal persists, and meansconnected to said repeater group for propagating a characteristic signalindicating the simultaneous reception of a spacing signal by said rstand said second repeaters.

8. A direct current half-duplex telegraph repeater, means in saidrepeater for transmitting a rst spacing signal through said repeater ina rst direction, a double-space by-pass circuit connected to saidrepeater, a transmitting device in said circuit, a time delay controlconnected to said device for controlling the transmitting of protractedsignals from said device, means in said repeater for receiving a spacingsignal incoming to said repeater from a second direction, While said rstspacing signal persists, means interconnecting said repeater and saidby-pass circuit for impressing said second spacing signal on saidby-pass circuit, and means connected to said by-pass circuit forpropagating a protracted signal from said transmitting device inresponse to said second spacing signal.

9. A direct current half-duplex telegraph repeater comprising areceiving relay, a receiving break relay and a sending relay, anarmature, a marking contact and a spacing contact on said sending relay,a telegraph channel extending from said armature through a line windingon said receiving relay and a line Winding on said receiving break relayin series, a biasing path extending from said armature through a biasingWinding on said receiving relay and a biasing Winding on said receivingbreak relay in series, a potentiometer connected to said biasingWindings, means comprising said potentiometer for controlling saidreceiving relay and said receiving break relay so that said receivingbreak relay will respond to a spacing signal incoming to said repeaterfrom said channel while said armature engages its spacing contact andwhile said receiving relay remains unresponsive to said signal.

l0. A half-duplex repeater in accordance with claim 9 and a double-spaceby-pass circuit including a first and a second transmitting device andmeans connected to said devices for actuating said devices for intervalsof substantially differing durations connected to said repeater forpropagating said spacing signal incoming from said channel.

11. A half-duplex repeater in accordance with claim 9 and a double-spaceby-pass circuit comprising a timing device for protracting said spacingsignal incoming from said channel.

12. A half-duplex multiway regenerative repeater, a double space by-passcircuit including signal element protracting means and means forflexibly interconnecting said repeater and said by-pass circuit.

KARL E. FITCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,334,551 Hanley Nov. 16, 19432,337,886 Hanley Dec. 28, 1943

